1. Field of the Invention
The present invention relates to a vacuum circuit breaker, and in particular to an improved terminal structure for a vacuum circuit breaker capable of lengthening the life of a terminal. In addition, the present invention relates to improving transfer of heat by effectively radiating heat generated in a terminal away from the terminal when electrifying the vacuum circuit breaker.
2. Description of the Conventional Art
Generally, a vacuum circuit breaker connects or interrupts current between a power source and a load of high voltage and current, for example, over thousands of voltages and of hundreds amperes. A circuit breaker also includes a switching mechanism in a vacuum chamber in order to effectively shield an arc produced when switching the vacuum circuit breaker.
As shown in FIGS. 1 and 2, a conventional vacuum circuit breaker is generally provided with a switching mechanism 10, a switching actuator 20 for operating the switching mechanism 10, and other subsidiary apparatuses (not shown).
The above described elements will now be described with reference to the accompanying drawings.
First, the switching mechanism 10, electrically connecting or interrupting between a power source and a load, is disposed in a vacuum chamber 11.
A movable contactor (not shown) in the vacuum chamber 11 is engaged with the switching actuator 20 of the vacuum circuit breaker. Therefore, when the vacuum circuit breaker is on, the movable contactor is in contact with a fixed contactor (not shown) in the vacuum chamber 11. When the vacuum circuit breaker is off, the movable contactor is separated from the fixed contactor by a predetermined distance.
The switching actuator 20 is disposed at a front side of the vacuum circuit breaker. The switching actuator is a mechanism for actuating an on/off switching operation of the movable contactor.
The subsidiary apparatuses which assist the vacuum circuit breaker to operate normally are provided with a control apparatus (not shown), constructed with the switching actuator 20. The control apparatus receives an external electrical signal and indicates an on/off state of the vacuum circuit breaker as the electrical signal. In addition, the subsidiary apparatuses include a leading apparatus 30 for enabling a terminal of the vacuum circuit breaker to be connected with or separated from a power source terminal or a load terminal, and an interlock (not shown) for securing the leading apparatus 30.
In addition, 40a is a source terminal, 40b is a load terminal, 50a is a source terminal bushing, and 50b is a load terminal bushing. Current from a substation is transmitted to power consumers by passing through the source terminal bushing 50a and the source terminal 40a, the load terminal 40b and the load terminal bushing 50b, via the switching mechanism 10. A safety shutter 51 closes and opens the source terminal bushing and load terminal bushing 50a, 50b. A cradle 52 guides a wheel 12 of the vacuum circuit breaker.
The source terminal 40a which is connected with the switching mechanism 10 and connected with or separated from the source terminal bushing 50a, will now be described with reference to FIGS. 3 to 6.
As shown therein, a flat terminal 42 connected with the switching mechanism 10 is welded to an one end of a cylindrical terminal 41. On a front surface of the cylindrical terminal 41, a plurality of screw fastening grooves 41a are provided.
There is provided a fastening plate 44 in which a plurality of screw fastening holes 44b are formed so as to be connected to the front surface of the cylindrical terminal 41.
A plurality of insertion grooves 44a for inserting a plurality of contactors 43 are disposed along an outer circumferential surface of the fastening plate 44. At least one fastening plate 44 may be provided.
Each of the contactors 43 is formed with a plurality of fixing grooves 43a on upper surfaces of each end thereof for respectively fixing a plurality of ring springs 45 therein. The contactors 43 are also formed with an insertion groove 43b at one side of a lower surface thereof so as to cooperate with one of the insertion grooves 44a, respectively.
A connecting process of the conventional terminal 40 will now be described.
First, the flat terminal 42 is welded to the one end of the cylindrical terminal 44. The fastening holes 44b of the fastening plate 44 respectively correspond with the fastening grooves 41a formed on the front surface of the cylindrical terminal 41. The fastening plate 44 is fastened with a screw 46 to the cylindrical terminal 41.
Each of the contactors 43 is inserted into a corresponding one of the insertion grooves 44a of the fastening plate 44 engaged with the cylindrical terminal 41.
When the ring springs 45 are respectively fitted in one end of the fixing grooves 43a formed on the upper surfaces of both ends of each contactor 43, each contactor 43 is firmly fixed due to elastic forces of the ring springs 45 which work inwardly. The ring springs 45 are then fitted in the other end of the contactors 43 to complete the process.
When the conventional terminal is electrically connected to the source or load terminal bushing, the heat generated in the terminal may not be effectively radiated.